The present invention relates to an antenna device with group antennas that are given narrower main lobes in the horizontal plane in a simpler way than what has previously been known.
Group antennas are a type of antennas that comprise a plurality of radiating elements, usually arranged in M rows and N columns. A common type of group antennas, here called column antennas, have considerably many more rows than columns, which gives a column antenna an antenna beam that is wide in the azimuth (sideways direction) and narrow in the vertical direction.
In connection, for example, with mobile telephony, it is usual to arrange column antennas side by side in a way that gives the required coverage. As a column antenna has a wide antenna beam in the sideways direction, there is a relatively high probability that a large number of sources of interference will be situated within the antenna beam, and the wide antenna beam means that it is difficult to direct the transmission only to the intended subscriber(s).
One way of suppressing sources of interference is to use information from antenna modules with overlapping antenna beams, with associated receivers for the antenna modules. As receivers are expensive, it can be of interest to give the antennas a narrower antenna beam. A known way of obtaining a narrower antenna beam in the sideways direction is to feed several column antennas via a shared feed network, which gives the column antennas a combined antenna beam which is narrow. A disadvantage of this is, however, that the distribution network results in an additional cost, and that the antennas involved must be combined in a way that is difficult.
There is thus a need to be able to give a column antenna in an antenna device a narrow main lobe in a way that is simpler and cheaper than what has previously been known.
This need is fulfilled by the present invention by providing an antenna device comprising a group antenna with radiating elements in M rows and N columns, where N less than M, in other words a column antenna. The group antenna has a width measurement and a height measurement, and is so arranged in the antenna device that the extent of the group antenna in a sideways direction projected in a horizontal plane, exceeds the width measurement of the group antenna, whereby the group antenna is given a narrower main lobe in the horizontal plane.
By the group antenna, the column antenna, being given a narrower main lobe in the horizontal plane, the statistical probability of receiving transmissions from sources of interference in or around the horizontal plane is reduced, and it is easier to direct the transmissions of the group antenna to one or more intended subscribers.
A group antenna arranged according to the invention can be incorporated in an antenna device incorporating a further number of group antennas with N*M radiating elements, where the additional group antennas also have a width measurement and a height measurement, and where the group antennas are arranged on the antenna device along a line that is circular or part of a circle, in such a way that their main lobes cover a required area. The additional group antennas are also arranged in such a way that their respective projections in a sideways direction in the horizontal plane exceed the width measurements of the respective group antennas, whereby the additional group antennas are also given narrower main lobes in the horizontal plane. In this way, an antenna device is created with a number of lobes that are narrow in the horizontal plane, without any shared distribution network needing to be used.